The present invention relates to a light shielding structure for shielding light, for example, to a light shielding structure for use in light shielding among a plurality of lens barrels of a camera provided with a zooming function.
Conventionally, with a light shielding seal forming a light shielding structure such as a zoom lens section or the like of a camera of this type, a strong force is not applied to the seal itself and sliding is performed at a relatively low speed and less frequently compared with an oil seal or the like.
As a structure conventionally known, there are, for example, (1) a light shielding seal of oleo-silicone rubber, (2) a light shielding seal of silicone rubber coated with PTFE, (3) a light shielding seal of oleo-silicone rubber baked on a metal fitting and (4) a light shielding seal of silicone rubber coated with PTFE which is baked on a metal fitting.
FIG. 11 shows the light shielding seal of (4). In FIG. 11, a light shielding seal 100 is configured by adhering a seal lip section 101 consisting of a ring of silicone rubber coated with PTFE and a reinforcing section 102 consisting of a metal ring as a metal fitting.
An end of a seal bore of the seal lip section 101 is provided on a diameter that is slightly smaller than an outer diameter of a lens barrel 200.
Then, in use, the lens barrel 200 is inserted into the seal bore and the seal lip section 101 is deformed in an L shape and closely adhere to the lens barrel 200 by its tensile force, whereby light and dusts are prevented from entering the seal bore when the lens barrel moves back and forth in zooming in and out and light shielding property and sealing property are given.
In this way, the conventional light shielding seal realizes decrease of a sliding resistance by impregnating the seal lip section with oil or coating it with PTFE.
However, in the case of the above-mentioned conventional art, the following problems occur.
In recent years, a compact camera has been miniaturized and realizes multi-functionality. On the other hand, an amount of an electric power from a power source of the compact camera is limited, thus reduction of an electric power is intended for each unit.
Under such circumstances, with the conventional light shielding seal, however much effort is consumed to reduce a sliding resistance by impregnating the light shielding seal with oil or coating it with PTFE, its reducing effect is limited due to sliding by the lens barrel and the light shielding seal that are solids contacting with each other. For example, even with the above-mentioned light shielding seal of (4) having a relatively low sliding resistance, a sliding resistance per piece is large at 20 to 100 gf.
Since the sliding resistance of the light shielding seals is large as described above, a relatively large amount of an electric power is consumed during zooming.
On the other hand, when a lens barrel expands and contracts, since a space for installing a light shielding seal varies according to an eccentric quantity of the lens barrel, if an eccentric quantity is large, a light shielding seal is crushed where the space for installing a light shielding seal is small and a gap arises where the space is large and thus leakage of light occurs even if the entire light shielding seal is made of rubber.
Thus, with a conventional light shielding device, it is required to provide a space S that is equal to or larger than an eccentric quantity on an outer diameter side of a light shielding seal as shown in FIG. 11 even if the light shielding device is intended to be miniaturized. The light shielding device is configured such that, if a lens barrel is eccentric, this space S absorbs an eccentric quantity to prevent a function of the light shielding seal from being deteriorated as shown in FIG. 12.
In addition, in some cases, a lens barrel has a flash (parting line) on a parting surface, from which light leaks.
The present invention has been devised in order to solve the above-mentioned problems of the conventional art, and a technical subject of a first aspect of the present invention to provide a light shielding structure that is capable of reducing a sliding resistance and at the same time improving light shielding property and further realizing saving of a space.
It is another technical subject of a second to fourth and fourteenth aspects of the present inventions to provide a light shielding structure that is capable of securing a larger power for holding magnetic fluid and shielding light more surely.
It is another technical subject of a fifth aspect of the present invention to provide a light shielding structure that is capable of securing a larger power for holding magnetic fluid and effectively absorbing an error even if an error of assembling or the like occurs among a plurality of members.
It is another technical subject of a sixth aspect of the present invention to provide a light shielding structure that is capable of further improving a light shielding effect.
It is another technical subject of seventh and eighth aspects of the present invention to provide a light shielding structure that is capable of securing a larger power for holding magnetic fluid and shielding light more surely.
It is another technical subject of a ninth aspect of the present invention to provide a light shielding structure that is capable of performing light shielding surely among lens barrels in a camera having a plurality of lens barrels.
It is another technical subject of a tenth aspect of the present invention to provide a light shielding structure of a lens barrel of a camera in which a lens barrel is easily.
It is another technical subject of an eleventh aspect of the present invention to provide a light shielding structure that is capable of effectively absorbing the error even if an error occurs in an axial centers of lens barrels of a camera.
It is another technical subject of a twelfth aspect of the present invention to provide a light shielding structure that is capable of effectively preventing dusts from entering the inside of a lens barrel from the outside.
It is another technical subject of a thirteenth aspect of the present invention to provide a light shielding structure that is capable of holding magnetic fluid surely in a position of magnetic force generating means without allowing the magnetic fluid contacting a lens barrel to flow away even if the lens barrel of a camera moves forward or backward.
It is another technical subject of a fourteenth aspect of the present invention of the present invention to provide a light shielding structure that is capable of preventing wetting of magnetic fluid when it contacts a member and further improving light shielding property.
In order to attain the above-mentioned technical subject, the first aspect of the present invention is a light shielding structure, which is provided among a plurality of members arranged spaced a predetermined distance apart to be movable relatively to each other and is capable of preventing light from entering from gaps which are formed among these plurality of members, comprising magnetic force generating means arranged in any one of the above-mentioned plurality of members and magnetic fluid which is magnetically held by this magnetic force generating means and contacts the other member and shielding the gaps which are formed among the above-mentioned plurality of members with the above-mentioned magnetic fluid.
Here, the magnetic force generating means refers to a so-called magnet, and the magnetic fluid refers to fluid in which ferromagnetic particulates are steadily dispersed by causing a surface-active agent to be adsorbed on the surface of the magnetic particulates. Base oil of hydrocarbon, fluorine, silicone or the like mixed with magnetic particulates having a surface-active agent adsorbed there on is used as the magnetic fluid. With these magnetic particulates of a predetermined density, a required light shielding property can be appropriately realized in relation to a thickness dimension in a light shielding direction of the magnetic fluid. Since this magnetic fluid is formed in a shape along a shape of the magnetic lines that are generated from the magnetic force generating means and contacts the other member, light from the outside is shielded. In addition, since the magnetic fluid is held by the magnetic line of force, it keeps a predetermined shape.
In addition, since the above-mentioned other member contacts the magnetic fluid, a sliding resistance can be reduced remarkably compared with a conventional sliding resistance due to a contact among solids. As a result of reducing the sliding resistance in this way, a power consumption that is required for relative movements of two members is reduced and an electric power can be saved.
In addition, even in the case in which a space for installing a light shielding seal varies due to eccentricity of the two members or the case in which there is a flash (parting line) on the parting surface, since the magnetic fluid moves following a magnetic field distribution to fill a gap between two members, eccentric follow-up property is improved and light can be completely shielded.
Moreover, as a result of improving the eccentric follow-up property, it is no more necessary to provide a space equal to or larger than an eccentric quantity on an outer diameter side of a light shielding seal as in the past, saving of a space can be effectively realized, in particular, in a compact camera that is required to be miniaturized.
The second aspect of the present invention is that the above-mentioned magnetic force generating means is formed in a shape that allows magnetic forces to concentrate in the direction to the above-mentioned other member.
Therefore, in the second aspect of the present invention, since magnetic forces are concentrated in the direction to the other member, the magnetic fluid is formed in a shape along magnetic lines of force and maintained by the concentrated magnetic forces, as a result, contacts the other member in a more strongly pressed state.
As a result, even if any one of the members moves relatively to the other member, situation of contacting magnetic fluid being dragged by the moving member can be reduced, whereby the light shielding property can be further improved.
The third aspect of the present invention is that the above-mentioned magnetic force generating means is formed in a point shape protruding in the direction to the other member.
Therefore, in the third aspect of the present invention, if the point shape of the magnetic force generating means is formed to protrude toward the other member, since a surface tension of magnetic fluid 4 and 8 can be formed larger compared with the case in which the tips of the magnetic generating means 2, 3 and 5 are flat, the magnetic fluid 4 and 8 can be held on the magnetic force generating means with a larger holding power. As a result, it becomes possible to shield light more surely.
The fourth aspect of the present invention is that porous materials are disposed in the above-mentioned magnetic force generating means 2, 3 and 5.
Here, for example, woven fabric, nonwoven fabric and the like fall into the category of the porous materials. If such porous materials are disposed, magnetic fluid is more firmly held on the magnetic force generating means by a capillary force of the porous materials in addition to a holding power by a magnetic force, whereby it becomes possible to shield light more surely.
The fifth aspect of the present invention is that the above-mentioned other member is formed of a nonmagnetic material.
According to the fifth aspect of the present invention, if the magnetic fluid takes a shape along magnetic lines of force by a magnetic force from the magnetic force generating means, the magnetic fluid is eventually pressed against the nonmagnetic material.
Therefore, even if an assembling error or the like occurs between one member and the other member, the error can be effectively absorbed.
The sixth aspect of the present invention is that the above-mentioned other member is formed of a magnetic material.
Therefore, according to the sixth aspect of the present invention, since the above-mentioned other member is formed of a magnetic material, not only the magnetic material but also the other member is attracted to the above-mentioned magnetic force generating means by a magnetic force and the magnetic fluid does not take a form of magnetic lines of force but is crushed to be deformed, whereby a contacting area with the other member can be made larger.
As a result, in the sixth aspect of the present invention, a light shielding effect can be further improved.
The seventh aspect of the present invention is that magnetic fluid holding means consisting of a magnetic body are provided on both sides of the above-mentioned magnetic force generating means and the above-mentioned magnetic fluid is magnetically held by the magnetic force generating means and the magnetic fluid holding means.
Therefore, in the seventh aspect of the present invention, since the magnetic fluid is magnetically held not only by a magnetic force generated from the magnetic force generating means but also by the magnetic fluid holding means, the magnetic fluid is held more firmly.
The eighth aspect of the present invention is that the above-mentioned magnetic fluid holding means is formed in a shape that allows magnetic forces to concentrate on the side of the other member.
Therefore, in the eighth aspect of the present invention, since magnetic lines of force concentrate in a part of the magnetic fluid holding means that is positionally closer to the other member, the magnetic fluid takes a shape along the magnetic lines of force and, as a result, an amount of contact of the magnetic fluid to the side of the other member can be increased.
Therefore, in the eighth aspect of the present invention, light can be shielded more surely.
The ninth aspect of the present invention is that the above-mentioned plurality of members are lens barrels of camera lens, and the above-mentioned magnetic force generating means is fixed over the entire circumference of the inside surface portion of the lens barrel on the outer side and the magnetic fluid contacts over the entire circumference of the outside surface portion of the lens barrel on the inner side to shield gaps between the lens barrel on the outer side and the lens barrel on the inner side.
Therefore, in the ninth aspect of the present invention, for example, even if the lens barrel on the inner side moves forward and backward in zooming the camera, since the magnetic fluid that is magnetically held by the magnetic force generating means fixed over the entire circumference of the lens barrel on the outer side is arranged in a state of contacting over the entire surface of the outside surface portion of the lens barrel between the lens barrel on the outer side and the lens barrel on the inner side, light is shielded by the above-mentioned magnetic fluid between the lens barrel on the outer side and the lens barrel on the inner side.
The tenth aspect of the present invention is that the above-mentioned magnetic force generating means and magnetic fluid holding means are fixed in advance to a metal member to be equipped in the end portion of the above-mentioned lens barrels.
Therefore, in the tenth aspect of the present invention, a light shielding structure in which lens barrels are easily manufactured can be provided.
The eleventh aspect of the present invention is that the magnetic force generating means and magnetic fluid holding means are arranged spaced apart from an inner circumference surface portion of the above-mentioned lens barrel on the outer side.
Therefore, in the eleventh aspect of the present invention, since the magnetic force generating means and the magnetic fluid holding means are arranged spaced apart from an attaching section formed in the inner circumference surface portion of the lens barrel on the outer side, a slight gap is formed between the magnetic force generating means and the magnetic fluid holding means and the attaching section formed in the inner circumference surface portion of the lens barrel on the outer side.
As a result, for example, even if axial centers are slightly deviated due to a manufacturing error, an assembling error or the like of lens barrels of a camera lens, the above-mentioned gap portion can absorb the above-mentioned error, whereby it becomes possible to make the axial center of each lens barrel to coincide with each other, that is so-call centering can be performed.
The twelfth aspect of the present invention is that a shielding member that can prevent dusts from entering from the outside is provided on the outer side of the above-mentioned magnetic fluid holding means.
Therefore, in the twelfth aspect of the present invention the claim 12, the above-mentioned shielding member can prevent dusts from entering from the outside. As a result, a situation in which dusts entering from the outside are held between the magnetic fluid holding means and the other member, rubbed against the other member and thus increases a sliding resistance and causes an increase of power consumption of a camera can be prevented.
The thirteenth aspect of the present invention is that a groove of a shape that allows magnetic fluid to be held in the position of the magnetic force generating means by a relative rotational motion of the lens barrel on the inner side and the lens barrel on the outer side is cut on the tip portion of the above-mentioned magnetic force generating means or the above-mentioned magnetic fluid holding means or on the outside surface of the lens barrel on the inner side.
Therefore, even if the other member moves relative to the one member, the magnetic fluid contacting the other member always stays in the position of the magnetic force generating means by the above-mentioned groove without flowing to be attracted by the other member.
As a result, in the thirteenth aspect of the present invention, light can be shielded more surely.
The fourteenth aspect of the present invention is that surface film processing that can secure oil volatilizing property is applied to the surface of the other member that the above-mentioned magnetic fluid contacts.
Here, for example, the case in which an oil volatilizing solid film is formed on the surface of the other member and the case in which oil that is incompatible with the oil forming the magnetic fluid is applied to form an oil film fall into the category of the surface film processing that can secure the oil volatilizing property.
In the case in which such processing is applied to the surface of the other member, even if the magnetic fluid contacts or slidingly contacts the other member, since the magnetic fluid becomes less likely to wet the surface of the lens barrel on the inner side, the magnetic fluid does not easily flow, whereby a light shielding seal can be formed more surely.